This invention relates to an apparatus for coating containers such as bottles, and also relates to a bottle conveying body.
Plastics bottles (which are predominantly made of PET) are being used to an increasing extent in the beverage industry. The disadvantage of plastics bottles as regards their unavoidable permeability, which permits the escape of carbon dioxide and the ingress of atmospheric oxygen, is countered by making plastics bottles of multi-layered construction in order to build up a barrier effect, or by spraying or vapour-coating them.
In a spraying apparatus which is known from DE 24 29 222 A, brackets which are aligned towards the conveying bodies are provided on a conveying track which is parallel to but separate from the conveying track of the conveying bodies. Each of these brackets bears a covering element. Cam drive mechanisms which cooperate with fixed guide tracks swivel each covering element, which is first of all held in a passive position, towards a bottle holder which is incorrectly fitted with a bottle to be sprayed. Upstream of the bottle discharge region, covering elements which are situated in their covering positions are swivelled back into the passive position again. Each covering element functions as a bottle detector, in that when the associated bottle holder is correctly fitted with a bottle the covering element comes into contact with a bottle before the movement into the covering position and is intercepted without the cam drive being able to effect a movement into the covering position. In this manner, a bottle holder which is incorrectly fitted is prevented from being sprayed and soiled in the spraying station. The additional cost of construction for a separate conveyor track for the covering elements and for controlling the movement thereof is considerable. Moreover, the bottles have to conveyed through the spraying station suspended vertically in order to ensure the correct cooperation of the conveying bodies with the covering elements, which makes it difficult to spray or coat the bottles correctly.
Additional prior art is contained in WO98/40531 (PCT/US98/05293) and DE 198 07 032 A.
The underlying object of the present invention is to provide an apparatus of the type cited at the outset and a bottle conveying body which is suitable for this apparatus which are distinguished by their simplicity of construction and by their high reliability in operation. In part, the object is also to be able to orient the bottles in the optimum positions each time during their transfer to and removal from the conveying bodies and during their transfer into the coating station, without impairment by the operation of the covering elements.
Since each conveying body of a bottle holder in the apparatus functions both as a support for and as a conveyor of the covering element, this results in a considerably reduced cost of construction for the apparatus, despite the protective function of the covering elements. The covering elements, which are disposed on the conveying bodies, are accurately aligned towards the associated bottle holders at every stage of operation, so that they perform their covering function very reliably and are able to protect the bottle holder or the region of the bottle holder from unwanted contamination by coating substances when no bottle is present. This simplification of construction is accompanied by a considerable reduction in overall space requirement. Mounting the covering elements on the conveying bodies only necessitates slight modifications to proven constructional designs, so that it is even possible for conveying bodies which are already in operation to be retrofitted with covering elements.
The bottle holder of the bottle conveying body holds the bottle in different orientations, which are the optimum orientations in each case, on the transfer or removal thereof of and in the coating station. These changes in position between different orientations are utilized by the covering element, which is actuated by the force of gravity, in order to cover a bottle holder which is incorrectly fitted with a bottle in the coating station, if need be. The use of the force of gravity as the driving force for the covering element enables costly drive control devices to be dispensed with. The system is operationally reliable, requires only a low extent of maintenance, and is cost-effective. Conveying bodies which are already in use can be retrofitted with covering elements at any time. No appreciable constructional modifications to the conveyor track or the coating station are necessary.
The center of mass of the covering element is displaced in relation to the swivel- or pivot bearing so that the force of gravity is able to move the covering element between the passive and covering positions and can hold it in the respective position. A separate drive mechanism for the covering element is therefore unnecessary.
The change in position of the conveying body during its movement along the conveyor track is advantageously utilized as a drive pulse for displacing the covering element Moreover, the force of gravity is used in order to hold the covering element in its correct position each time.
It is advantageous for the conveying body to be oriented with an approximately vertical bottle holder during the transfer or discharge of bottles, but is advantageous for the bottle holder to be orientated approximately horizontally in the coating station. During the rotational movement of the bottle about its longitudinal axis which is normally executed, its horizontal position in the coating station results in complete coating of the bottle surface, while with a vertical orientation the feeding or discharge of bottles can be effected without problems in a constricted overall space.
It is advantageous if the bottle holder is disposed so that it can move on a mouth aperture of the conveying body, and if the covering element possesses a closure part which fits into or on to the mouth aperture. In the covering position, the entry of coating substances or spray substances and any contamination of the bottle holder and its surroundings in the conveying body are thus effectively prevented.
The covering element is formed in a constructionally simple manner as a flap which is mounted on the conveying body on one side of the bottle holder and which can be swivelled to and fro, preferably by at least 90xc2x0.
The flap can be a simple sheet metal or plastics plate to which the swivel pin is fixed by a flat, wherein pin journals of the swivel pin are held in bearing bores in bearing blocks fixed to the conveying body. The swivel pin divides the flap into a displacement part and a covering part, and the covering part is either made longer and or has a concentrated mass, in order to distance the center of mass from the swivel pin with the longest lever arm possible.
In order to keep the resistance to swivelling of the flap as low as possible, the bearing bores and/or the pin journals should be made of a material and which facilitates sliding or should be coated with a material which facilitates sliding. If necessary, even the bearing blocks as a whole can be made of a plastics material which facilitates sliding. The regions of movement of the swivel pin in the bearing blocks are advantageously screened off.
In order to increase operational reliability, it may be advantageous for at least one ballast weight to be disposed on the flap, which then places the center of mass as far as possible away from the swivel pin.
In one embodiment, the flap automatically functions as a bottle detector which holds the flap in the correct position for the action of the covering element displacement apparatus when the bottle holder is correctly fitted with a bottle. The displacement apparatus is formed by a fixed guide along the conveyor track which only acts on the displacement part of the flap when a bottle is present on the bottle holder and which holds the flap in the passive position in which it does not contact a bottle which is rotating in a spraying station.
In an alternative embodiment, the covering element is acted upon by an energy storage device, towards the covering position at least. The covering element again functions as a bottle detector, in that when a bottle is correctly present on the bottle holder it assumes a position in which the fixed guide of the covering element displacement apparatus can act on the covering element. However, if a bottle has not been placed on the bottle holder, the energy storage device then moves the covering element into the covering position so that the guide of the displacement apparatus does not act on the covering element at all. An obvious measure is the provision of a further displacement apparatus, upstream of the removal region of the conveyor track, which moves covering elements which are situated in their covering positions back into their passive positions again for the renewed takeover of bottles.
In a further alternative embodiment according to claim 12, the covering element is biased in a bistable manner both towards the passive position and towards the covering position, on whether a covering element overshoots a dead center in one direction of movement or in the other. At at least one point on the conveyor track, the covering element displacement apparatus acts on the covering element, the bottle holder of which has not received a flask, in order to move the latter beyond the dead center towards the covering position. The energy storage device brings the covering element into the covering position and holds it in the covering position until the covering element displacement apparatus is again effective locally. In this embodiment, a guide for the covering element, which maintains its respective position automatically, does not need to be provided along the major part of the conveyor track.
It is advantageous if the covering element displacement apparatus is brought non-positively into engagement so that it only brings the covering element into the covering position if the bottle holder has not received a bottle. However, if the bottle holder has been correctly fitted with a bottle, the resistance to movement which occurs due to the contact between the covering element and the bottle impedes the movement of the covering element into the covering position, and the covering element then maintains its passive position automatically without any external influence.
In a further alternative embodiment, a drive mechanism for the covering element, which acts in one direction or in both directions, can be provided on the conveying body, and is actuated depending on whether or not a bottle has been fitted correctly on the bottle holder. The respective actuation is derived from the operation of the bottle detector. In this respect, the bottle detector can not only operate mechanically, but can also operate in a contactless manner by an optical, pneumatic or inductive route, in order to generate the requisite drive signals for the drive mechanism. Switching magnets or permanent magnets and/or a hydraulic or compressed air cylinder can be used as a driving mechanism, If the driving mechanism is of bistable design, then a short drive pulse after takeover of the bottle or before takeover of the bottle is sufficient in each case in order to move the covering element into its correct position.